Method of and apparatus for making open hearth steel



M. J. CONWAY Feb. 2, 1937.

METHOD OF AND APPARATUS FOR MAKING OPEN HEARTH STEEL Filed Aug. 5, 19554.Sheets-Sheet 1 FIG 1 INVENTOR.

'6 Wzag g ATTORNEY.

Feb. 2, 1937. M. J. coNwAY METHOD OF AND APPARATUS FOR MAKING OPENHEARTH STEEL Filed Aug. 5, 1935 4 Sheets-Sheet 2 FIG 2 INVENTOR. M7

ATTORNEY.

M. J. CONWAY .Feb., 2, 1937.

METHOD OF AND APPARATUS FOR MAKING OPEN HEARTH STEEL Filed Aug. 5, 19554 Sheets-Sheet 5 ATTORNEY.

Feb. 2, 1937. M. J. CONWAY 2,069,196

METHOD OF AND APPARATUS FOR MAKING OPEN HEARTI-I STEEL Filed Ag. 5,19.35 1 4 Sheets-Sheet 4 ooooooooo oooooooo INVENTOR.

ATTORNEY.

Patented Feb. 2; 1937 METHOD OF AND APPARATUS- FOR MAKING OPEN HEARTHSTEEL Martin J. Conway, Coatesyille, Pa.

Application August 5, 1935, Serial No. 34,692

7 Claims. .'(01. 263-15) This invention relates to method of andapparatus for making steel by the open hearth process, and the presentapplication is a continuation in part ofv an application seriallynumbered 731,456 filed June 20, 1934, which has matured as Patent Number2,027,151 granted January 7, 1936.

. It is among the objects of the invention to provide an open hearthfurnace which shall employ 10 unidirectional firing for which purposepreheated air is supplied by recuperators through which the products ofcombustion of the furnace are drawn in heat exchange relation with theair delivered to the furnace to support combustion.

Another object of the invention is the provision of means forautomatically regulating the air supply to the burners and consequentlyto different portions of the hearth independentlyof and in addition tothe volume and regulation of air supplied through the recuperators.

. In the aforementioned copending application, the recuperator structureper se and its coacting function with the furnace is' particularlyfeatured, and the present application is directed pri-' g5 marily to thefurnace characteristics beneficial to the metallurgical process by whichthe melting and refining of the steel is carried out.

While it has been heretofore proposed to melt ores and iron inunidirectional fired reverberatory furnaces, I am unaware of any attemptheretofore made to commercially apply this method of firing in themaking of steel by open hearthpro'cess. u I I am familiar with patent toFitch No. 1,735,608 granted November 12, 1929 which discloses twinfurnaces with .a common air preheat device of therecuperator type,thistype of furnace being recommended for melting iron which'is attemperatures approximately 300 less than the tem- 4Q peratures employedfor the melting of steel.

I am also familiar with patent granted to Barbanson et al. No. 1,030,152granted June 18, 1912 which is for a unidirectional fired open hearthfurnace especially usefulin the firing of coal-dust.

This patent does not disclose any method of preheating the air and infact recommends the utilization of air in merely aslightlyheated'condition. v v

My open hearth furnace structure differs from these unidirectional firedprior art devices in the arrangement of hearth and roof structureswhich, in cooperation with the burners at one, end, spaced toselectively heat the bath of metal, and the gas duct at-the opposite endand through various other regulable control auxiliaries, is conducive toeffectively and efficiently refine steel with minimum loss ofheat and aminimum consumption of fuel." I

For metallurgical purposes, the heat application by continuous firingis-desirable as-it permits 5 of better regulation and application ofheat to the entire surface of the bath, which obviates the disadvantagesinherent in the reversing regenerator type of open hearth furnaces;Thus,

for example the bath is not submitted to alternate 1 oxidizing andreducing atmosphere. In my unidirectional firing type furnace, the aircan be definitely measured to suit the fuel volume for producing, withinlimits, a desired degree of oxidizing or reducing atmosphere. Iteliminates air 15 infiltration and lends itself to absolute stack draftcontrol. By unidirectional firing, erosion-- and abrasion of therefractories are confined to one end of the furnace while the burner endmaintains its shape and proportions indefinitely. 20

.The heat transferred to the bath for metallurgical reactions is undercontrol at all times because of the steady temperature of the incomingair which, all in all, increases the rate of production of the furnace,lowers the refractory costs 25 perton of the refined metal with aconsequent reduction in the cost of the product.

These and other features of the invention will become more apparent frdma consideration of the accompanying drawings constituting a part 30hereof in which like reference characters designate like parts and inwhich:

Fig. -1 is a plan view of a furnace embodying the principles of thisinvention;

Fig. 2 a vertical section taken on the line 2-2, i 1;

Fig. 3a similar view taken on the line 33, Fig. 1;

Fig. 4 a similar view taken on the line 4-4, m Fig. 1;

Fig. 5 a horizontal section-taken on the lines 5-5, Figs. 3 and 4;

Fig. 6 a vertical section taken on the line 68, Fig. 1. 45 Withreference to Fig. 2 of the "drawings, the

reference numeral l designates the permanent hearth upon which'the basichearth materials are supportechcharging doors 3 and tap hole 4 beingprovided to respectively charge and discharge the furnace hearth; Thehearth-2 is formed with sloping sides 20 which, in cooperation with theroof 5, constricts the-furnace chamber at the respective ends so thatthe enlarged central heating chamber of the furnace per- 5 I mits ofexpansion of the fuel gases as their prod- 'ucts of combustion aredeveloped. To this end,

an especially enlarged portion is provided by the sawtooth-shapedportion 6 of theroof above the velocity of the products of combustionwhich,

-. ing from the recuperator structures as will'be through the graduallyreducing area of the furnace, pass out of the duct 1 communicating witha slag pit Ia leading to a series of recuperator structures as will behereinafter explained.

Burners 8 and 9 project through the burner ports in the end wall androof of the furnace respectively and are disposed to apply or project aflame streamto blanket first the hearth for sintering before the. hearthis charged with scrap metal, pig iron; etc., and for reducing the chargeand blanketing the bath during the melting and refining periods of theprocess. Burners 8 and 9 are supplied by a common fuel line l0 and haveindividual regulating valves II and l2 to control the fuel supply to therespective burners. The burners 8 and 9 are disposed in air ducts I3 andI4, respectively, which supply the preheated air from a commonduct |5leadhereinafter'%scribed. The air ducts 3 and M are provided withdampers |3a and Ma to obtain individual regulation of the air supply tothe several burners.

On account of the intense heat developed in the furnace chamber, it isdesirable to cool. the refractory constituting the furnace roof, and tothis end the structural supports l6, which con stitute hangers for theroof, are covered wit sheet metal I! to constitute a circulating spacefor a cooling medium such as air which is drawn into the open ends l8and I9 by a forced draft created by an exhaust duct 20. To providecooling in the event of failure of the exhaust means, side doors 2|and'a ventilator 22 are provided for setting up a natural draft throughthe ingress of air which. is circulated by the convection currentsproduced by hgat radiation through the roof refractory. Other means offorced cooling of the furnace roof will be hereinafter described. i p

The functional character of the furnace of Fig. 2 is briefly; the firingof the furnace chamber atone end and the withdrawal of the products ofcombustion from the opposite end, the

control of combustion and the velocity of theproducts of combustionthrough the dimensional variations of the roof and hearth spacing. Theregulation of. the preheat to support combustion and produce desirableoxidizing and reducing designate recuperators through which 1thew'astegases are drawn at gradually reducing temperaconditions will behereinafter described'in con- 7 nection with the detailed description ofthe auxiliary apparatus, a plan view of which is shown in Fig. 1 of thedrawings. v In Fig. 1, .reference characters 25, 26 and 21 tures, therecuperator structures 25 and 26 consisting of refractory tile and isthe primary. re-

and 21 arecommunicative through chamber 36.

Duct 3i communicates with a stack 32 to which f of the recuperator.

the products of combustion may be passed directly from recuperator 26 orafter passing through recuperator 21 by duct 33, a suction fan 34 beingprovided for this purpose.

The air ducts 13 and I4 surrounding theburners 8 and 9 communicatethrough manifolds 35 and 36 with a common duct 31, one end of whichpasses to the preheat air chamber of recuperator- 25 to which air issupplied by a blower 38, having .an air duct 39 leading. to the bottomof the recuperator tile structure, as shown in Fig. 3

of .the drawings, and having another air supply. pipe 46 communicatingwith an injector 4| dis-' fto maintain a balance of pressure on bothsides of the recuperator tile for reasonsghereinafter explained.

Air is supplied through the To prevent the development of pressurediiferentials, a regulator 42 is provided, the regulator being of awell-known type that is connected by tubes 43 and 44 to the air andwaste gaspa'ssage Ihe regulator is connected by suitable control means45 in thecircuit of motor 46 that drives the blower 38 to regulate theoper'ation'of the blower to balance the pressures in the recuperatorpassages.

Duct 26 for circulating the coolingair in the chambr above the: roof bydrawing air through the end openings l8 and I9 may be utilized to supplyair under pressure by the blower 50, having conduit connection 5| withduct 20, which connection is provided with a gate valve 52. Duct 26 alsoconnects through conduit 53 with a blower 54 that delivers the air drawnfrom the space 'above the roof of the furnace to the recuperator 21 whengate 55 is open, and gate 52 is closed.

A' regulating damper 56,is provided in conduit 53 and a d'oor5'| whichis opened when damper 55 is closed and blower 50 is operated.

Figs. 3 to 6 inclusive show in detail the, air and gas flow passagesthrough recuperators 25, 26 and 21 in which the air duct 31, Fig. 3, isshown communicating with an air collecting chamber 60 at the top of therecup'erator' tile 6| of the.

is shownconnected to the air passage 29.lead-' ing from rccuperator 26torecuperator 25. In

Fig. 5', the double arrows indicate the movement I of the waste gasesorproducts of combustion after leaving the collectingchamber Ia at thebottom of the furnacefiue or duct I, and the single arrows indicate thedirection of move- ,ment of air supplied to the heat exchange tile 6|from recuperator 26.

The tile in the recuperator by the numeral 62' and the movement of thewaste gases and air are designated by the double and single arrows,respectively. The metal construction of the recuperator 21 is designatedby the numeral 63, 64 being the waste'gas passages and the spacingbetween the members 63 being the air passages as indicated by the singlearrow. Bailles .65 are provided in the metallic recuperator to divertthe direction of air fiow as shownQthus assuring maximum contact of theair withthe heat exchanging elements. p,

The operation of the above described apparatus is briefly as follows:

With particular reference to Figs. 1 and 2,

26 is designated is charged through the side openings 3, but as thesurface 2 of the hearth is renewed-for each charge, the flame fromburners 8 are directed to blanket the hearth material with a sheet offlame to sinter the material preliminary to delivering the charge to thechamber. When the tion or waste gases generated in the furnace chamberare withdrawn through flue 1, and by virtue of the divergent path of thegases, the solid particles are precipitated and settled in collectingchamber Ia, thus permitting the free gases to pass into the entirestructure of the recuperator 25, from whence it passes through duct 28'to recuperator 26, thence through chamber 3!! to recuperator 21 fromwhich it"is exhausted through conduit 33 by blower 34 and delivered tothe stack 32'. I

"The air to support combustion may be preheated initially by being drawnover the roof of the furnace beneath the covering material II where itsheat exchange relation with the refractories of the roof portions 5 and6 produces a preliminary heating of the air which is withdrawn by blower54 through the duct 20 and de-. livered to the recuperator 21. It isthen conducted through the recuperator 26, duct 29 to recuperator 25,and finally passes through duct 31 to the manifold 35 and 36 of theburner ports whence it emerges to envelope the burner tips and minglewith the fuel to form a combustible mixture.

- If it is desired to utilize forced cooling of the furnace roof underconditions of excessive heating of the roof refractories, gate 55 ofduct 20 is closed, door 51 opened and the blower 54 draws air from theatmosphere and delivers it to the combustion.

recuperator 2'! from which it is transmitted to the recuperators 26 and.25 as previously explained and as shown by arrows in Figs. 3 to 8inclusive of the drawings. Gate 52 of conduit 5| is then opened andblower 50 delivers air under pressure to duct 20 which carries it to thechamber constituted between the top of the roof of the furnace and thecovering sheet material l1. Under these conditions, the end openings l8and I9 may be closed to cause the air to leak through the crevices ofthe roof refractories,

. force cool the refractories and protect the roof against the excessiveheat of the".products of If the forced cooling is either by circulatingair, by exhaust means or delivering air by pressure means, the generator22 is opened as are the side doors 2|.

To prevent damage to the recuperator tile by any pressure differentialcaused by air pressure and gas pressure in the tile structure regulator42 by controlling. the blower 38 'will maintain a balancedpressure bydelivering more of less air to the furnace thereby varying the volumeand pressure of the products of combustion passing through therecuperator tile. Such balanced pressure will prevent distortion of thetile structure with consequent leakage resulting in the products ofcombustion being recirculated through the preheat air duct to thefurnace chamber.

' By regulating the burner valves H and I2 and air supply dampers |3aand Ma for the delivery of the volume of the preheated air and thetemperature thereof, an oxidizing or reducing atmosphere may be createdin the furnace chamber to produce the metallurgical conditions for thebath of metal supported upon the hearth 2. The importance of suchregulation is obvious to one skilled in the art, and in addition thelocation of the burners 8 and 9 will direct the flame to blanket thebath and to furnish an adequate supply of heat to all portions ofthebath. By

regulation of the fuel supply to the individual burners and the volumeand temperaturebf-the preheat, any temperature condition may be readilyobtained in the melting and refining chamber. When the metal has beenrefined, it is withdrawn from the tap hole 4 into an ingot pouring ladleor other suitable receptacle.

Because of the facilities for definitely measuring the air, the furnacemay be fired by a variety of fuels and a definite quantity of air can besupplied for a given quantity of fuel to produce any degree of oxidationor to provide a desirable reducing atmosphere, required and best suitedto the condition of the bath. .The stack draft control of this furnace.will cut down oxidation losses and heat transfer losses, both in thebath and recuperator. The destruction of the refractories by erosion andabrasion is confined to the exhaust end of the furnace which can readilybe replaced while the burner end is maintained in shape and proportionsindefinitely, thus avoiding costly replacement and rebuilding of thesecomplicated parts of the furnace. The heat transferred to the bath formetallurgical reactions is under control at all times by controlling thetemperature of the incoming air and the refining of the bath is greatlyexpedited with a consequent reduction in the tonnage cost of thefinished metal.

While in my former application I am claiming the features of pressurebalance and temperature control and regulation effected through therecuperators and their controls, I am herein claiming thecharacteristics of the furnace per se or in combination with certainfuel, air and waste gas regulating devices or parts.

I claim:

1. In an open hearth furnace, a hearth, side walls and roof, forming aheating chamber enlarged intermediate its ends to constitute a pluralityof combustion compartments, one of which is elevated with respect to theother, burner openings to said compartments communicating with a sourceof preheated air, burners projecting into said compartments through saidopenings inclined to impinge flame streams against the ma terialsupported on the hearth, a common exit for the products of combustionremote from said means for opening said cooling chamber and forcirculatingair therethrough by withdrawing the air therefrom, said airbeing thereby heated, burner ports at one end of the furnace chamber, awaste gas passage at the opposite end, means for closing said coolingchamber and for delivering air under pressure therein, and means ventingthe cooling chamber when the pressure cooling means is inoperative.

3. In an open hearth furnace. a hearth, side walls and roof forming afurnace chamber, said roof being off-set'atone end to form a plurality Iend wall of saidfurnace chamber and burner of combustion compartments,burner ports in the ports in the'ofi-set portion of the roof, burners insaid ports, a common waste gas passage at the end'of the furnace-chamberopposite'said burners and ports,'said burner ports communicating with asource of preheated air, means for independently regulating thetemperature and volume of theair supplied to said burner ports, andmeans for independently regulating the fuel supply to the burners at theend and'in theofiset portion of the furnace roof whereby indee'pendently,regulable heat zones are established in selective portions ofthe furnace chamber.

-4. An open hearth furnace structureias set forth in the next precedingclaim characterized by the burners at the end of the chamber beingdisposed to project a heat fiame parallel with'a portion of the furnacehearth and in the direction of a waste gas passage, and the burnersinthe off-set portion of thefurn'ace roof being inclined to. impinge aflame stream substantially centrally of the furnace hearth and in thedirection of the waste gas passages.

5. The method of treating steel in an openhearth furnace consisting inthe application of a plurality of flame streams spaced longitudinallyand transversely of the furnace chamber at. one end thereof to blanketthe bath supported by the furnace hearth, supporting combustion in thefurnace chamber by a regulable quantity of pre-' 1 heated air, andmaintaining the temperature of the preheated'air .constant'during theentire treating period. 5

6. An open hearth furnace comprising a melting hearth having slopingsides and forming the bottom wall ofan enclosed heating chamber, the

roof of said chamber having an inverted vshaped portion to provide anenlarged combustion area, a burnerport inone wall ofvsaid furnace atsubstantially the level of the hearth and aburner port disposed throughthe off-set portion of the roof. constituted by one leg of theinvertedvgsaid port being spaced a substantial distancehoriz'ontallly of thefirst named port, the roof and hearth remote from the ports graduallyconverging to form a common exhaust passage for the products ofcombustion at the end of the heating chamberopposite the burner ports,and means for independently regulating the fuel -and'preheated airsupplyto'said ports.

, 7. In an open hearth furnace, a hearth, side.

